When trying to change router bits, the old one won't come out of the collet. You can't get enough of a grip on either piece to get them apart.

Hold a nail set against your benchtop with the tip pointing up. Then, put the open bottom of the collet over the nail set and push against the router-bit shank. Tap the shank end against the nail set until the bit breaks loose.
—From the WOOD® magazine shop